Process for producing artificial silk from viscose



Patented Nov. 21, 1933 oFFicE PROCESS FOR PRODUCING ARTIFICIAL SILK FROM VISCOSE Theodoor Koch, Arnhem, Netherlands, assignor,

by mesne assignments, to American Enka Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Application May 19, 1931, Serial No. 538,629, and in the Netherlands May 23,

4 Claims.

In my concurrent patent application No. 520,482 a process is described for making artificial silk from viscose according to which small quantities (less than 2% and more than 0.05 cal- 5 culated on the viscose) of a sulphonated fatty acid or of a sulphonated fat having a sulphonation degree of 100% are added at any stage of the viscose production, whilst the quantity of the nonsulphonated free fatty acid which may be pres- 19 ent or of the non-sulphonated fat is in every case so small that the product gives no cloudiness with excess of alkali. It was further found to be advantageous to have small quantities of alkylated aromatic sulphonic acids present as well in the viscose.

It has now been found that the addition of sulphonated fats, oils or fatty acids with a sulphonation degree of 100% in amount of less than 2% and more than 0.05%, calculated on the vis- 20 cose, at any stage of the production of viscose, in

which the same has not yet reached the ordinary state of ripeness, involves particular advantages. By a degree of sulphonation of 100% I intend one in which all the fatty acid radicals present are bound to sulphuric acid. The amount of any non-sulphonated, free fatty acid present is to be so small, that the product upon addition of an excess of alkali shows no turbidity. However, small amounts of alkylated, aromatic sulphonic acids can be present in the viscose in spinning according to the new process. Such sulphonation products can be obtained for instance by processes such as described in British Patents Nos. 493,480 and 293,717. If the addition substances are added at a stage of the viscose production in which the viscose has not yet attained the otherwise usual ripening stage of 9-l0 Hottenroth, then a viscose treated in this way may even in the unripened state, he spun to lustrous and compact artificial silk in acid, e. g.

sulphuric acid precipitating baths, in which otherwise milky silk is produced. Here again the addition of the said addition substances can also be effected in any desired stage of the viscose production, but, as is necessitated by the nature of things, always prior to and before the viscose has attained the otherwise normal ripening stage. In these circumstances the viscose may be spun practically without any preliminary ripening even directly after dissolution of the xanthate, or in any desired subsequent stage also, e. g. at l5l'l Hottenroth, or even in the particularly dangerous transitional stage of 10-14 Hottenroth. The generally usual acid baths, sulphuric acid, so-called Muller baths, or even other sulphuric acid baths, may be employed as spinning baths.

It has also been found that the process leads to a further additional advantage if it is combined with the stretching of the viscose silk during the production process known per se. Generally speaking, it is true that the strong stretch ing of the viscose silk during the ordinary production process entails considerable enhancement of the strength properties, but, on the other hand it frequently also involves an undesirable strong lowering of the extension value. It has now been found, however, that if, with assistance of the said additions to the viscose, the stretching of the viscose silk during the spinning process is in addition effected with viscose in an unripened stage, according to the invention, then not only can a noteworthy raising of the strength be produced, but a satisfactory extensibility is maintained as well.

What I claim is:

1. A process for the production of artificial silk from viscose consisting in adding small amounts, viz, less than 2% and more than 0.05%, calculated on the viscose, of a sulphonated fatty so acid with a sulphonation degree of 100% at any stage of the viscose production in which the viscose has not yet attained the normal ripening stage, the amount of non-sulphonated free fatty acid or non-sulphonated fat which may be press5 ent being so small that the viscose shows no turbidity with an excess of lye, and in spinning the unripened treated viscose in acid precipitating baths.

2. A process for the production of artificial silk from viscose consisting in adding small amounts, viz, less than 2% and more than 0.05%, calculated on the viscose, of a sulphonated fatty acid with a sulphonation degree of and a small amount of alkylated aromatic sulphonic 95 acid at any stage of the viscose production in which the viscose has not yet attained the normal ripening stage, the amount of non-sulphonated free fatty acid or non-sulphonated fat which may be present being so small that the shows no turbidity with an excess of lye, and in spinning the unripened treated viscose in acid precipitating baths.

3. A process for the production of artificial silk from viscose consisting in adding small amounts, viz, less than 2% and more than 0.05%, calculated on the viscose, of a sulphonated fatty acid with a sulphonation degree of 100% at any stage of the viscose production in which the viscose has not yet attained the normal ripening viscose 10o amount of alkylated aromatic sulphonic acid at any stage of the viscose production in which the viscose has not yet attained the normal ripening stage, the amount of non-sulphonated free fatty acid or non-sulphonated fat which may be present being so small that the viscose shows no turbidity with an excess of lye, and in stretch spinning the unripened treated viscose in acid precipitating baths.

THEODOOR KOCH. 

